Investigation of heat transfer and joule-thomson effect in wells of depleted oil and gas reservoirs used for carbon dioxide (co2) storage

Abstract

This study investigated the heat transfer mechanisms and the Joule-Thomson effect at the wellhead while storing carbon dioxide (CO₂) in depleted oil, gas, and coal reservoirs. It was assumed that the injected CO₂ for storage is in a singlephase pure state. In the reservoir well, convection heat transfer along the wellbore and conduction heat transfer with the surrounding rock soil were analysed during the production of CO₂ to the surface. Additionally, the cooling effect at the wellhead caused by the Joule-Thomson effect was examined. A positive value of the Joule-Thomson coefficient indicated the presence of a cooling effect. For the production well, the study considered temperatures of 30, 51, and 78 °C, pressures of 3.8, 4.3, and 6.1 MPa, and well depths of 1000, 1700, and 2600 meters. Six different rock-soil types surrounding the production well at the reservoir head were included, with a thermal gradient of 25 °C/km and a CO₂ flow velocity of 1 m/s. The calculated difference in conduction and convection heat loss between the wellhead entry and exit ranged from 23.918 to 481.980 W. The Joule-Thomson coefficient was found to vary between 6.797 and 17.91 0C/MPa, depending on the depth, temperature and pressure of the well. The change in exergy efficiency due to the Joule-Thomson effect (throttling exergy) was calculated to vary between 3.042 and 10.766.